Robert Cesnjevar

First successful implantation of a biodegradable metal stent into the left pulmonary artery of a preterm baby

Stent implantation in the youngest patients with a congenital heart disease implicates limitations concerning further vessel growth, the need of staged redilation, and later surgical removal. The search to overcome these restrictions led to open stent designs, with a wide adaptability to the vessel growth and recently to the development of bioabsorbable stent materials. A preterm baby born at 26 weeks of gestation was referred to our clinic following inadvertent ligation of the left pulmonary artery. Despite efficient debanding, the left lung perfusion was absent. Implantation of a biodegradable 3 mm magnesium stent was performed in a hybrid procedure when the baby weighed 1.7 kg. Reperfusion of the left lung was established and persisted throughout the 4‐month follow‐up period during which the gradual degradation process of the stent completed. Additional interventions, should they become necessary, seem not to be limited. Despite the small size of the baby, the degradation process was clinically well tolerated. The mechanical and degradation characteristics of the magnesium stent proved to be adequate to secure reperfusion of the previously occluded left pulmonary artery. Bioabsorbable stents with different diameters may help develop new strategies in the therapy of vessel stenosis in pediatric patients.

Early failure of xenogenous de-cellularised pulmonary valve conduits — a word of caution!

OBJECTIVE The longevity of valved right ventricle to pulmonary artery (RV-PA) conduits is limited due to calcification and degeneration of non-viable structures. Xenografts are commonly used because of the restricted availability of cryopreserved homografts. Tissue-engineered (de-cellularised) pulmonary valves (TEPVs) were thought to be a valuable alternative to cryopreserved pulmonary homografts due to postoperative seeding with viable autologous vascular endothelial cells. METHODS From July 2007 to December 2008, xenogenous TEPV (Matrix P plus) were implanted in 16 patients in the right ventricular outflow tract for different indications, related to congenital heart disease. Mean age at operation was 14+/-11 years, including three patients younger than 1 year. The median conduit size was 22 mm (range: 13-26 mm). RESULTS The early and late survival rates were 100%. At a median follow-up of 10 months (range: 2-17 months), six patients (38%) had to be re-operated upon due to obstructed grafts. Five of these patients were older than 13 years (range: 13-26 years); one patient was younger than 1 year. On echocardiography before re-operation, mean systolic gradient in the main PA was 66+/-18 mmHg. In explanted conduits, we found a predominantly peripheral conduit narrowing without leaflet calcification. Histological examination revealed stenosis formation, due to inflammatory infiltration and severely fibrogenic pseudo-intimal reaction. CONCLUSIONS On the basis of our short-term results, the Matrix P plus de-cellularised tissue-engineered pulmonary valve cannot be regarded as an ideal conduit for right ventricular outflow tract reconstruction, as the widespread use of these grafts may increase the possibility of frequent early conduit failures.

Kit Regulates HSC Engraftment across the Human-Mouse Species Barrier

In-depth analysis of the cellular and molecular mechanisms regulating human HSC function will require a surrogate host that supports robust maintenance of transplanted human HSCs in vivo, but the currently available options are problematic. Previously we showed that mutations in the Kit receptor enhance engraftment of transplanted HSCs in the mouse. To generate an improved model for human HSC transplantation and analysis, we developed immune-deficient mouse strains containing Kit mutations. We found that mutation of the Kit receptor enables robust, uniform, sustained, and serially transplantable engraftment of human HSCs in adult mice without a requirement for irradiation conditioning. Using this model, we also showed that differential KIT expression identifies two functionally distinct subpopulations of human HSCs. Thus, we have found that the capacity of this Kit mutation to open up stem cell niches across species barriers has significant potential and broad applicability in human HSC research.

Early obstruction of decellularized xenogenic valves in pediatric patients: involvement of inflammatory and fibroproliferative processes

BACKGROUND Decellularization of pulmonary valve substitutes is believed to eliminate immunogenicity and improve conduit durability. This study focused on a detailed histopathological and immunohistochemical analysis of explanted Matrix P plus valves, following their early obstruction in pediatric patients. METHODS Occurrence of fibrosis, scar formation, neovascularization, and inflammatory infiltrates were determined in longitudinal sections of four valve specimens explanted after 12-15 months. Valves were immunohistochemically analyzed for presence of different subtypes of inflammatory cells. The expression of smooth muscle actin and connective tissue growth factor was determined. RESULTS We observed a foreign body-type reaction accompanied by severe fibrosis and massive neointima formation around decellularized porcine valve wall, whereas the equine pericardial patch remained separated from porcine layer and acellular. Re-cellularization of decellularized matrix was low, and neovascularization was observed only in the neointima and scar tissue. Inflammatory infiltrates, composed mainly of T cells, B cells, and plasma cells, as well as the presence of dendritic cells, macrophages, and mast cells were detected in the tissue surrounding the porcine matrix. In the fibrous tissue, overexpression of connective tissue growth factor was observed. The leaflets remained functional, with normal endothelialization and no degenerative changes. Control pre-implant samples of Matrix P plus valve revealed incomplete decellularization of porcine matrix, which may have contributed to increased immunogenicity of these conduits. CONCLUSIONS Early obstruction of decellularized Matrix P plus valve is associated with massive inflammatory reaction and exaggerated fibrotic scaring around porcine conduit wall. Detailed studies will be necessary to determine factors that contribute to remnant immunogenicity of decellularized grafts.

Human lymphoid organ dendritic cell identity is predominantly dictated by ontogeny, not tissue microenvironment

Transcriptional identity of human dendritic cell subsets is mainly dictated by ontogeny rather than by signals derived from the cells’ final tissue microenvironment. Dendritic cell branches Dendritic cell (DC) subsets have been well studied in mice; however, the relative contribution of ontogeny and tissue microenvironment to DC function in humans is less clear. Now, Heidkamp et al. perform phenotypic and transcriptional profiling of three DC subtypes in different human tissues from a large number of individuals. They find that DC subpopulations in more lympho-hemaotopoietic organs (spleen, thymus, and blood) are more strongly influenced by ontogeny, whereas those from lung and skin may be influenced by the issue microenvironment. The data collected here provide an in depth look at the transcriptional profile of dendritic cell subsets in humans and inform our understanding of human DC biology. In mice, conventional and plasmacytoid dendritic cells (DCs) derive from separate hematopoietic precursors before they migrate to peripheral tissues. Moreover, two classes of conventional DCs (cDC1 and cDC2 DCs) and one class of plasmacytoid DCs (pDCs) have been shown to be transcriptionally and functionally distinct entities. In humans, these three DC subtypes can be identified using the cell surface markers CD1c (cDC2), CD141 (cDC1), and CD303 (pDCs), albeit it remains elusive whether DC functionality is mainly determined by ontogeny or the tissue microenvironment. By phenotypic and transcriptional profiling of these three DC subtypes in different human tissues derived from a large number of human individuals, we demonstrate that DC subpopulations in organs of the lymphohematopoietic system (spleen, thymus, and blood) are strongly defined by ontogeny rather than by signals from the microenvironment. In contrast, DC subsets derived from human lung or skin differed substantially, strongly arguing that DCs react toward modulatory signals from tissue microenvironments. Collectively, the data obtained in this study may serve as a major resource to guide further studies into human DC biology during homeostasis and inflammation.

Cystatin C and neutrophil gelatinase-associated lipocalin: biomarkers for acute kidney injury after congenital heart surgery.

QUESTIONS UNDER STUDY To evaluate the diagnostic value of serum Cystatin C and urine neutrophil gelatinase-associated lipocalin (NGAL) for the detection of acute kidney injury in patients undergoing congenital heart surgery. METHODS Serial samples of serum Cystatin C and urine NGAL were collected from 139 consecutive patients with congenital heart defects aged 3 days to 30 years after admission to the intensive care unit, 2 and 6 hours after the end of cardiopulmonary bypass. Biomarker levels were compared to perioperative data retrospectively. Acute kidney injury was defined according to the paediatric-modified RIFLE classification. RESULTS According to the paediatric-modified RIFLE criteria 53% of patients developed evidence of acute kidney injury. Serum Cystatin C concentrations were strongly correlated with severity of acute kidney injury. Optimal sensitivity of 80% and specificity of 66% for the prediction of acute kidney injury occurred at a cut-off value of 0.995 mg/l, 2 hours after the end of cardiopulmonary bypass. The 2 hour urine NGAL concentration was significantly correlated to the duration of cardiopulmonary bypass, time of aortic cross clamping, and serum lactate concentration. Moreover a significant correlation was found between urine NGAL and both length of hospital stay and mechanical ventilation. CONCLUSIONS In patients after congenital heart surgery, urine NGAL indicates the damaging force of cardiopulmonary bypass and serum Cystatin C is a valuable predictive biomarker for resulting acute kidney injury.

Search for somatic 22q11.2 deletions in patients with conotruncal heart defects

A wide range of clinical variability in patients with 22q11.2 deletions has been demonstrated in numerous studies. Nevertheless, it is still an open question if major genetic factors contribute to clinical expression. Therefore one aim of this study was to investigate, if patients with 22q11.2 deletion and conotruncal heart defects show a “second hit” somatic 22q11.2 deletion in tissue from the conotruncus, heart vessels or thymus. The second aim was to analyse patients with conotruncal heart defects without 22q11.2 deletion in blood cells for somatic deletion mosaicism. We were able to study tissue samples from heart surgery from 23 patients, 9 of whom had 22q11 deletions by FISH analysis on metaphase spreads from peripheral lymphocytes. Analysis of 18 polymorphic markers from the 22q11.2 region in DNA prepared from thymus and/or heart vessels and/or conotruncus tissue and peripheral lymphocytes in each patient did not show any allelic loss. Thus somatic 22q11.2 deletions apparently do not play a major role in conotruncal heart defects in patients with or without germ line 22q11.2 deletion.

Comparative study on the migration of di-2-ethylhexyl phthalate (DEHP) and tri-2-ethylhexyl trimellitate (TOTM) into blood from PVC tubing material of a heart-lung machine.

Medical devices like blood tubing often consist of PVC material that requires the addition of plasticizers. These plasticizers may migrate into the blood leading to an exposure of the patients. In this study the migration behavior of three different blood tubing sets (PVC material with two different plasticizers and silicone as control material) applied on a heart-lung machine standardly used for cardiopulmonary bypass (CPB) in children was studied. We analyzed the total plasticizer migration by analysis of both, the parent compounds as well as their primary degradation products in blood. Additionally, the total mass loss of the tubing over perfusion time was examined. The PVC tubing plasticized with DEHP (di-2-ethylhexyl phthalate) was found to have the highest mass loss over time and showed a high plasticizer migration rate. In comparison, the migration of TOTM (tri-2-ethylhexyl trimellitate) and its primary degradation products was found to be distinctly lower (by a factor of approx. 350). Moreover, it was observed that the storage time of the tubing affects the plasticizer migration rates. In conclusion, the DEHP substitute TOTM promises to be an effective alternative plasticizer for PVC medical devices particularly regarding the decreased migration rate during medical procedures.

Recombinant Factor XIII Reduces Severe Pleural Effusion in Children after Open-Heart Surgery

Chylous effusions frequently occur after cardiac surgery due to severe damage to the lymphatic system, thus indicating that the insertion of a chest tube may be necessary. Factor XIII (FXIII) is discussed as being essential for wound healing. The aim of this retrospective study was to evaluate whether the application of a single dose of FXIII results in a reduced amount of pleural effusion, leading to an earlier release of patients from the hospital. The cases of 40 children with severe chylous effusions after open-heart surgery were examined. Twenty patients received FXIII and were compared to 20 age- and weight-matched patients who did not receive FXIII. Major parameters included the amount of effusion before and 1 and 3 days after the application of FXIII; the duration of chest tubes; the total amount of fluid loss via drainage; and the period of hospitalization. FXIII levels in plasma showed an inverse correlation with fluid loss. After application of a single dose of FXIII, a significant reduction of pleural effusion within the first 24 hours was detected. However, no difference was observed between the two groups when comparing the total amount of pleural effusions within the first 72 hours. Finally, the duration of hospitalization did not differ between the FXIII-treated and the control group. A single application of FXIII rapidly reduces the amount of chylous effusions in the early period after open-heart surgery. This effect is detectable only for 24 hours after the treatment and does not alter the further clinical outcome. Prospective clinical trials are warranted to determine if repeated application or a higher dose of FXIII may improve the clinical outcome of chylous leakages in children after open-heart surgery.

Posttraumatic aneurysm of the right atrium

We report on an acquired right atrial false aneurysm, which was removed under extracorporeal circulation. The patient remembered three occasions of blunt chest trauma with rib fractures. Clinical symptoms were ongoing dyspnea, chest pain, and atrial fibrillation.